
PROF, BACHE'S 



LECJIJRE 01 THE GULF. STREAM, 



[from the am. jour, of science and arts, vol. xxx, Nov. I860.] 



LECTURE 



ON THE 





GULF STREAM, 



Prepared at the request of the American Association 
for the Advancement of Science. 

By A. Df B ACHE 

it 

Supt. U. S. Coast Survey.* 



[Delivered before the American Association for the Advancement of Science, at 

Newport.] 



By request of the Association, at their last meeting, at Spring- 
field, I now present a summary of the results of the Gulf Stream 
explorations made by the officers of the Coast Survey. 

The Grulf Stream is the great hydrographic feature of the Uni- 
ted States coast, and no survey of the coast could be complete 
for purposes of navigation, without it. Hence the explorations 
have been early undertaken and thoroughly carried on. But as 
it required peculiar means and special adaptation in the officers 
to this line of research, and did not require a continuous survey, 
the work has been executed from time to time, as means and 
officers could be had without interference with the more regular 
operations of the hydrography. 

An act of Congress which refers to this Survey, requires the 
immediate presentation of its results to Congress and they have 
therefore been discussed as soon as procured and have been 
given to the public. 

This is the great sea mark of the coast of the United States, 
both Gulf and Atlantic, and its qualities as hindrances and aids 
to navigation require that the navigator should be well informed 
in regard to it. 

. i k * Communicated by the Author. 

1 



2 Prof. Baches Lecture on the Gulf Stream. 

In order to present an intelligible summary of the results ob- 
tained by the Coast Survey in the short time allowed for a lec- 
ture, it is necessary to condense the subject very considerably, 
to omit matters at all extraneous to the subjects in hand, and to 
confine ntyself to a brief and direct statement of the means em- 
ployed in examining the stream from its surface to its depths, the 
method of studying the results, and of the results themselves. 

The temperatures in and near the Gulf Stream, are among 
its most striking peculiarities, and therefore have formed one 
principal object of observation. It will be necessary in order to 
bring the subject within limits, to confine myself chiefly at 
this time to the consideration of this class of facts and to the 
results and laws connected with them. 

I shall proceed therefore to consider the subject under the fol- 
lowing heads : 

1. The Instruments for determining depths and temperatures 
and for obtaining specimens of the bottom. 

2. The plan of research. 

3. The method of discussion of the results, 

4. The results, consisting of type-curves of the law of change 
■of temperature with depth, at several characteristic positions. 
Type-curves showing the distribution of temperatures across the 
stream, represented by two sets of curves, one in which the vari- 
able temperatures at the same depth is shown, and the other in 
which the variable depth of the same temperature is represented. 
Upon the diagrams showing these latter curves, the figure of the 
bottom of the sea is given, where it has been obtained. 

Discussion in regard to the cold wall, which is one of the most 
interesting features of the approach to the Gulf Stream. 

5. The limit of accuracy of the results. 

6. The figure of the bottom of the ocean below the Gulf 
Stream. 

7. The general features of the Gulf Stream as to temperature. 
These points are illustrated by diagrams, enabling the eye to 

follow the results as they are stated. 

I. Instruments. 

1. For Temperatures.- — The instrument for determining temper- 
atures should fulfill the two conditions of registering its indica- 
tions and of being unaffected by pressure. The common mercu- 
rial thermometer, while it answers perfectly for the determination 
of temperatures at the surface, fails in both the conditions stated. 
The ordinary self- registering thermometer, or self-registering 
metallic thermometer, in the watch form, as made bj^ Breguet, 
Montandon, and Jiirgensen, when provided with a suitable cover 
to protect it from pressure, answers a good purpose, and has 
been extensively applied in the course of the observations. As 



I 



Prof. Baches Lecture on the Gulf Stream. 



a rule it is only the minimum temperature thermometers that 
must be used, as the temperatures decrease generally in descend- 
ing. An ordinary self- registering minimum thermometer placed 
in a glass globe, was successfully used by Commander Charles H, 
Davis, and by Lieut. Gr. M. Bache. It has the disadvantage of tak- 
ing the temperature slowly, and of being inapplicable below a 
certain depth. Small hollow cylindrical brass vessels which were 
divided in two parts closely fitted by grinding, and within which 
the Breguet thermometers of the watch form were placed, were 
an improvemenfrupon the glass globe, as taking the temperature 
of the sea more rapidly, but besides the difficulty of making the 
joint tight, they were crushed by the pressure, at even moderate 
depths. The substitution of a globe, for the cylinder, extended 
the range of these instruments, but the thermometers were often 
crushed or injured by the access of sea- water to the interior of 
the globe. Six 7 s self-registering thermometers as bearing con- 
siderable pressure without injury and without rendering the in- 
dications erroneous, and as requiring no case to enclose them, 
except to prevent breaking from accidental knocks in handling, 
are very useful. They are still favorites with many of the offi- 
cers, though others complain of their great liability to derange- 
ment f especially if the mercury is not perfectly clean, when the 
mercurial column easily separates and some skill is required to 
bring it together. These instruments are from their cheapness 
still furnished to the parties and are used successfully at depths 
reaching about one hundred fathoms, and on occasions, conside- 
rably lower. Keeping them in order requires the skill of an 
experimenter, rather than that of an observer, and hence they 
do not satisfactorily fulfill the conditions of the problem. The 
metallic thermometer of Joseph Saxton, Esq., of the U. S. Office 
of Weights and Measures, is a compound coil resembling some- 
what the well known instrument of Breguet. In its construc- 
tion, two stout ribbons, of silver and platinum — carefully united 
by silver solder to an intermediate thin plate of gold — are coiled 
with the more expansible metal in the interior. The gold serves 
to prevent the tendency of the silver and platinum to separate. 
The lower end of this coil is fastened to a brass stem passing 
through the axis of the coil, while its upper end is firmly at- 
tached to the base of a short cylinder. The whole motion of 
the coil as it winds and unwinds with variations of tempera- 
ture, thus acts to rotate the axial stem. This motion is magni- 
fied by multiplying wheels contained in the short cylinder at top, 
and is registered upon the dial of the instrument by an index y 
which pushes before it a registering hand, moving with suffi- 
cient friction merely to retain its place when thrust forward by 
the index hand of the thermometer. These instruments are 



4 Prof. Baches Lecture on the Gulf Stream. 

graduated by trial. The brass and silver portions receive a 
thick coating of gold by the electrotype process to prevent the 
action of the sea-water upon them. 

When kept clean by frequent washing in fresh water, and in 
good order and frequently compared with the standards to guard 
against accidental derangements, these thermometers answer ad- 
mirably all the required conditions. The length of the coil 
measured along its axis should not be less than six inches, as 
the interposition of wheels to magnify the motion, should as far 
as possible, be avoided. The water being alt around the coil, 
which is a good conductor, and has a low specific heat, the instru- 
ment readily feels the temperature of the part of the sea where 
it is exposed, and registers it to less than half a degree (say 
0*2) with certainty. The box which covers the coil and indica- 
ting part of the thermometer is merely to protect it from acci- 
dental injury, and is open so as to permit the sea-water to 
pass freely through it. Plate IV gives a view of Saxton's 
metallic thermometer, and of its various parts in detail. Al- 
though there seemed no reason to doubt that this instrument 
was free from any effects of pressure, it was deemed desirable to 
actually try it by extreme pressure and a series of experiments 
made by J. M. Batchelder, Esq., showed that at pressures less than 
that corresponding to 600 fathoms, the effect was less than one 
degree (0°'25 to 1°) and at pressures from 600 to 1500 fathoms 
the change amounted to little more than from 7° to 9° Fahr., the 
index returning when the pressure was removed. For great 
depths the effects of pressure must be ascertained, as it is specific 
in each instrument and probably depends chiefly upon some 
mechanical defect in the construction, perhaps in the soldering.* 

The apparatus used in these experiments on the effect of pres- 
sure, was a very ingenious one for testing hydraulic engines by 
Mr. Thomas Davison of the Novelty Iron Works of New York. 
Fig. No. 12, Plate IY. 

2. For Depths. — Where the depth becomes considerable the 
usual sounding line fails entirely to give it, especially if there is 
a current and more especially if there is besides, a counter-cur- 
rent. The amount of " stray line " is very variable. This sub- 
ject has been ably examined of late years by Commanders Maury 
and S. P. Lee, Lieuts. Berry man, Brooke and others of our navy, 
and by Commander Dayman and others of the British navy, 
and especially by Prof. Trowbridge of the Coast Survey in his 
memoir read before the Association (" Deep Sea Soundings," 
by AY. P. Trowbridge, Assistant U. S. Coast Survey,) at the 
meeting in Baltimore and re-published in the American Journal 
of Science and Arts, vol. xxviii for the year 1858. 

* Gulf Stream Explorations ; Third Memoir Proceedings Amer. Assoc. Adv. Sc, 
13th Meeting, Springfield, 1859, and this Jour., [2], vol. xxix, 1860. 



Prof. Baches Lecture on the Gulf Stream, 5 

The use of Ogden's or Ericcson's leads to 100 fathoms is still 
continued by some of the officers of the survey, though, at such 
depths, nothing better than the common sounding line is in fact 
required. Massey's lead with Woltman's wheel, as an indicator. 
has been extensively used of late years. Mr. Saxton's indicator 
is more simple than Massey's, but acts upon the same principle. 
To remedy the defect of the turning of the cord of the lead line, 
two indicators are applied, one on each side of the axis. Prof. 
Trowbridge's lead modified somewhat from that described at 
the last meeting of the Association in Baltimore, has recently 
been tried with good success by Lieut. Comdg. Wilkinson in the 
last soundings across the Straits of Florida for the telegraph to 
Havana. The most reliable observations heretofore made in the 
Coast Survey have been with Massey's indicator, the errors are 
not such as to affect the development of the laws of change at 
the moderate depth reached in most of the observations, and at 
great depths the changes are very slow. The new apparatus 
has the advantage of saving a great deal of time and therefore 
inaccuracies from change of position during the sounding are 
avoided. 

3. For obtaining specimens from the bottom. — The only satisfac- 
tory test of having reached the bottom of the sea at considerable 
depths being the bringing up of a specimen, this has been a sub- 
ject of constant study with us. The different instruments inven- 
ted by Lieut. Stellwagen, Commander Sands, Lieut. Craven, 
Lieut. Berryrnan, Lieut. Brooke and other officers of our navy, 
are all in use for different kinds of bottom, and according to the 
preference given by different hydrographic chiefs. The one 
most commonly used in these explorations has been Lieut. 
Stellwagen's invention ; a cup placed below the sounding lead, 
covered by a dick or valve of leather which slides up the stem of 
the cup and opens when the lead is descending, closing when it is 
raised. The weight of the lead and the turning of the cord gen- 
erally suffice to sink the cup into the bottom, filling it, and when 
the valve is made to close tightly by a piece of flexible leather 
below the stiff disk, the specimen is not washed out as the lead 
is drawn up. In Commander Sands' sounding apparatus a 
spring keeps an outer cylinder over an opening in an inner hol- 
low one, until it reaches the bottom, when the outer cylinder is 
forced upwards and the opening at the side of the inner one, 
which, having a conical termination, penetrates the bottom, per- 
mitting a specimen of the bottom to pass in. On raising the 
lead the spring forces the outer cylinder over the opening, pre- 
venting the specimen from being washed out. The only very 
deep soundings being, as a general rule, in soft bottom, Sands' 
specimen-cylinder is admirably adapted to that class of work. 



6 Prof* Baches Lecture on the Gulf Stream. 

II. Plan of the Work. 

The plan of the work was simple. The temperatures were to 
be ascertained at various depths, at different distances from the 
coast, on sections as nearly at right angles with the stream as 
practicable, the sections starting from some point well known in 
position. The temperatures were to be taken at distances di- 
minishing as the changes of temperature were more rapid. So 
in regard to the depths, the observations were to be multiplied 
in the strata of rapidly varying temperatures near the surface. 
So in regard to position, when the cold water near the coast was 
rapidly exchanging for the warm water of the Gulf Stream, the 
sections diminishing in distance as the source of the warm water 
was approached. 

The vessel's position was determined with reference to some 
prominent point, Sandy Hook, or Cape May, for example, the 
course run was perpendicular to the supposed axis of the stream, 
S.E., several positions were taken up in succession and at each 
the temperatures ascertained at the surface, at 5, 10, 15, 20, 30, 
50, 100, 200, 300, 400, 600 fathoms, or depths found to apply 
more satisfactorily under the general rule, to the position and 
section. Having crossed the stream any position found to be 
desirable, could be assumed on returning, and the extreme posi- 
tion reached was verified by the return to the coast. 

The summer season was selected for the standard observations 
for various reasons, but chiefly for two, namely, that the weather 
permitted more accurate work, and the phenomena were more 
likely to be those of equilibrium, when the surface water was 
more slowly changing its temperature. Our little vessels could 
not, without considerable danger, be exposed to the roughness of 
the wind and water in the Gulf Stream in winter, and when we 
attempted comparative winter observations, disappointment was 
often the result. The loss of one valuable officer and ten of his 
crew, and the extreme peril of another in autumnal explorations 
of the stream, has but too fully justified these precautions. The 
propriety of selecting the summer for making the observations 
was completely proved by the success in determining the laws of 
temperature. 

These observations were but incidental to the hydrography of 
the coast, and hence were prosecuted only when means could 
be spared from other more pressing and regular parts of the 
work. It was only a favorable conjuncture with regard to offi- 
cers, means, weather, adaptation of vessel, and the like, which 
gave results even when attempted. Too much, credit cannot be 
assigned to those who have succeeded in this laborious and per- 
ilous work, and their names have been kept in close connection 
with their results, whenever and wherever brought before the 
public, and they have been carefully preserved in the archives 



Prof. Baches Lecture on the Gulf Stream. 7 

of the Survey. Charles H. Davis, George M. Baclie, S. P. Lee, 
Kichard Bache, John K Maffitt, T. A. Craven, Otway H. Berry- 
man, B. F. Sands and John Wilkinson make up the list of our 
successful observers in this field within the last sixteen years. 
Their names you will see attached to the sections run by them 
on the general chart of the Gulf Stream presented to you this 
evening. 

The first was run in 1844, from Nantucket south and eastward, 
by Commander C. H. Davis, now the accomplished Superinten- 
dent of the Nautical Almanac, and the last in 1860 by Lieut. 
John Wilkinson, from the Tortugas, southeast to the coast of 
Cuba. The work still goes on perseveringly. 

The number of sections run has been fourteen, the number of 
positions on these sections occupied 300, and the number of ob- 
servations made for temperature 3600. The limits below which 
the stream and the adjacent waters have been explored for tem- 
peratures are from latitude 23° K., to 41° N., and from longi- 
tude 83° W. to 66%° W. from near Havana to near Cape Cod, 
and from the Tortugas to 9-J° E. of Cape Henlopen. The dis- 
tance along the axis of the Gulf Stream to the most north- 
eastern point in the North Atlantic, measures nearly 1400 nau- 
tical miles. 

III. Method of Discussion of the Results. 

These have generally been discussed by diagrams, sometimes 
by analytical formulas ; the former method is generally best adapt- 
ed to the character and degree of accuracy and circumstances 
of the observation ; the diagrams finally adopted after trials were 
chiefly of three different kinds, one for the discussion of the 
change of temperature with depths, the two others for the change 
of temperature with position as well as depth. Of the first of 
these diagrams Nos. 1 and 2, Plate I, are specimens. The depths 
constitute the ordinates and the temperatures the abscissas of a 
curve, showing the law of change of temperature with the depth. 
Upon the horizontal lines at the top of the paper the tempera- 
tures from ten degrees to ten degrees Fahr. are written and on 
the vertical line at the side, the depths. The separate observa- 
tions being represented by dots ; the curve is drawn with a free 
hand among them. 

The next two classes of diagrams give the distribution of tem- 
peratures across the sections. In the first the temperature cor- 
responding to the same depth ; in the second the depths corres- 
ponding to the same temperatures. In this latter the figure of the 
bottom is shown when ascertained. In both classes the distances 
from the cape, or headland, city or inlet, which is the origin of 
the section is marked, and the several positions occupied for ob- 
serving, so that the abscissas of the curve are the distances from 



8 Prof. Baches Lecture on the Gulf Stream. 

the point of beginning. In the first (see diagram Wo. 4, Plate I,) 
the temperatures are marked on the vertical lines at the left side 
of the diagrams, the ordinates of the curves thus corresponding 
to temperatures. In the second (see diagram No. 9, Plate I,) 
the depths are similarly written, the ordinates thus corresponding 
to depths. The notes or legend, show in the first case to what 
depths the curves correspond and in the second to what temper- 
atures. The observations at each position being plotted accord- 
ing to its temperature or depth in the two classes of diagrams, 
the curve is drawn with a free hand among the points. 

It should be observed that the discussion of each season's ob- 
servations was in general made separately, and that the result of 
one, two or three seasons, grouped, were announced separately, 
leaving to the new observations to confirm, or refute, the con- 
clusions drawn. It is a remarkable fact that with such difficul- 
ties in the way, in the character of the phenomena to be observed, 
in the diversity of seasons and of observers, the phenomena 
have always been readily deducible from the observations, and 
that the separate discussions have been confirmations, the follow- 
ing of the preceding; in short that the nature of the medium 
in which the work has been performed in its relations to heat, 
has more than compensated for other difficulties and that the 
results are more accordant than the elaborate ones obtained from 
the progress of temperature below the surface of the ground by 
the experienced and skillful observers who have made them. 
Few observations have been rejected in the whole series. 

I need not notice special diagrams which will be explained 
when your attention is called to them. 

When the character of the diagrams to be made had been 
definitely fixed, they were prepared under the direction of the 
chiefs of the parties, so that I was relieved of the personal labor 
of representing the results. In the subsequent general discussion 
I was greatly assisted by Prof. Pendleton, U. S. N. and by Prof. 
"W. P. Trowbridge, Assistant IT. S. Coast Survey, who has made 
a general review of the whole of the results preparatory to their 
publication in a volume of the Eecords and Kesults of the Coast 
Survey. 

IV. Results. 

1. Type-curves of law of temperature with depths at the most charac- 
teristic positions. — The two most characteristic positions are in the 
cold current between the land and the Gulf Stream and in the 
axis of the stream itself. 

1. Diagram No. 1, Plate I, is a specimen of the type-curve in 
the cold current. The long tongue from the surface to about 50 
fathoms in depth is the overflow of the warm water of the Gulf 
Stream, the temperature varying from 81° to about 55°. The 



Frof. Baches Lecture on the Gulf Stream. 9 

temperatures in the mass of water from 50 fathoms down to 500 
fathoms are just such as would take place in a mass of water 
heated by conduction from the surface, the law is that of a loga- 
rithmic curve, in which the conducting power of sea water is the 
modulus of the system. 

A comparison of many of these curves with the logarithmic 
form showed that it was applicable to them within the limits of 
the probable error of the observations. Taking the warm stra- 
tum from the Gulf of Mexico above and the cold polar stratum 
below, the mass of the water between is heated by conduction. 
The bottom of the sea has not been reached under the axis of 
the Gulf Stream, north of Cape Lookout on the North Carolina 
coast. 

This form of curve was deduced in 1844 from the observations 
of Commander Charles H. Davis and was the first discovery 
made in connection with the then recently commenced system- 
atic exploration of the Gulf Stream by the Coast Survey. 

2. Nos. 2, 3, and 3 bis, Plate I, are specimens of the type- 
curve in the Gulf Stream, taken from the sections off Cape Henry, 
Cape Hatteras and Charleston, being characterized by the com- 
paratively short beak or projection and the persistence of the 
higher temperature to great depths as 55° to 425, 450, 550 fath- 
oms giving the peculiar shape to this curve between 50 and 
500 fathoms. 

II. Type-curves of distribution of Temperature across the Stream. 

(a.) Curves of temperature at the same depths. — The sections 
made are the following, beginning the enumeration at the Gulf 
of Mexico : 1. Tortugas to Havana. 2. Sombrero Key to Salt 
Key. 3. Carysfort, L. H., to Cuba. 4. Cape Florida to Bernini. 
5. Off Cape Canaveral. 6. Off St. Augustine. 7. Off St. Si- 
mon's, Georgia. 8. Off Charleston. 9. Off Cape Fear. 10. Off 
Cape Hatteras. 11. Off Cape Henry. 12. Off Cape May. 13. 
Off Sandy Hook. 14. Off Cape Cod, being on the average one 
to each hundred miles along the axis of the stream. These are 
marked on the general chart, Plate III, the names of the ex- 
plorers being stated in the column which gives the point of 
origin of each section. 

The Sandy Hook curves, Nos. 4 and 5 Plate I, are among the 
best of the type-curves of temperature at the same depth, though 
among the earliest determined. The overflow of the Gulf Stream 
into the long space occupied by the cold current between it and 
the shore, mixing in a degree with the cold water, is well shown 
by the curves a, b and c at the surface, 5 and 10 fathoms, and the 
still greater admixture with the cold water at 20, 30 and 50 
fathoms (d, e, /.) The whole space from the shore to 240 miles, 
is occupied, however, with comparatively cold water. Then is 
2 



10 Prof. Baches Lecture on the Gulf Stream. 

met the sudden rise to the Gulf Stream shown especially below 
50 fathoms and termed so appropriately by Lieut. George M. 
Bache the "cold wall," that navigators have not hesitated to 
receive the term into use ; next the hot water of the Gulf Stream, 
rising to a maximum of 82°, then falling to a minimum of 80°, 
rising to a second maximum of 81J°, falling to a second mini- 
mum of 78° and rising from this toward a third maximum. 
With these results the curves at 5 and 10 fathoms and those at 
20, 30, 50, 70, 100 and 150 fathoms agree and, with characteris- 
tic differences, those of 200, 300, 400 and 500 fathoms. 

The cold wall at 20 fathoms shows a rise of 19° in 25 miles, 
three quarters of a degree to a mile, and at 200 fathoms of 16°, 
in the same distance ; at the surface it is nearly 8° in 50 miles. 
The cold water between the Gulf Stream and the shore has two 
well marked maxima and two minima in it, of which one seems 
to correspond in position to the sudden deepening of the water 
100 miles from Sandy Hook, as shown by the Coast Survey off- 
shore chart between Gay Head and Cape Henlopen. 

These results are more distinctly seen by grouping the curves 
into natural groups and taking the mean of their indications. 
Diagram No. 5 Plate I, gives the group of six curves from the 
surface to 30 fathoms, of four curves from 40 to 100 fathoms, 
both inclusive of 200, 300, and the single curve at 400. 

Similar groups are shown on Diagram No. 6, Plate I, from 
Cape Henry, the cold wall, three maxima of temperature and 
three minima being very distinctly seen. The results of three 
different explorations of this section, by three different officers, 
in three different years, are shown upon the same diagram. The 
coincidence of result could hardly be better. The average of the 
whole of the observations is shown in No. 6 bis, Plate I. 

The cold wall here gives a change of 22-^° in 50 miles from 
the curves between and 30 fathoms and 18° in 50 miles in the 
mean of 200, 300 and 400 fathoms. 

The average of the three years comes out beautifully on Dia- 
gram No. 6 bis, Plate I. The Charleston curves are shown 
upon No. 7, Plate I. They are less regular than those just given, 
for reasons which will appear, when I come to speak of the sec- 
ond class of diagrams. 

The conclusions deduced from the examination of all the 
sections between Cape Florida and Sandy Hook is, that the Gulf 
Stream is divided into alternate bands of hot, or warm and cool 
or cold water, the most distinct of which is that containing the 
axis of the Gulf Stream. 

That between the stream and the coast there is a fall of tem- 
perature so sudden that it has been aptly called the cold wall, 
less distinct at the surface and where the overflow from the Gulf 
Stream passes furthest toward the shore, but still distinctly 
marked even at the surface. 



Prof. Baches Lecture on the Gulf Stream. 11 

Navigators have noticed these changes of temperature and 
have supposed themselves at each occurrence of warmer water 
to be in the hottest water of the stream and so have been greatly 
embarrassed and have deemed the phenomena and limits of the 
Gulf Stream to be very irregular. 

The cold water between the Gulf Stream and the shore has 
also bands less regular than those beyond the axis of warmer and 
cooler water. 

The intrusive cool water in the Gulf Stream on the Sandy 
Hook section was distinctly recognized in 1816 by Lieut. Geo. M. 
Bache, who from the facts observed, supposed it to represent a 
division of the warm water of the stream into two branches. 

Passing through the Straits of Florida between the keys and 
reefs and the coast of Cuba we have after going beyond Cape 
Florida, a different type-curve. The cold wall is less distinctly 
marked and the rise of temperature is less marked. It rises how- 
ever to an axis near the coast of Cuba. Throughout the length of 
the Strait there is but one maximum of temperature and the 
bands belonging to the Atlantic regimen do not occur in the 
straits. (See diagrams Nos. 3, 4, 5, 6, Plate II.) The cause of 
this change of regimen will be seen in presenting the other form 
of diagram. 

(b.) Curves of depths at the same temperature. — I have selected 
curves from the southern portions of the work, partly because 
the bottom has been struck in the sections and the diagrams show 
its sections as well as those of the stream, and partly to show 
how fully the deductions in regard to the divisions of the stream, 
apply to these, as well as the more northern sections. The 
Charleston section of Lieut. Maffitt is given on diagram No. 9, 
Plate I. The surface curve, notwithstanding the disturbance by 
a storm, shows the cold wall, (see also No. 7) the axis and 
two other maxima, the corresponding minima, a maximum with- 
in the cold current which is not therefore, as has been supposed, 
cut off at Hatteras, the curve of 72° reaching to the coast and 
77° nearly reaching it. The Cape Florida diagrams (Nos. 3 and 
7, Plate II.) give two maxima with indications of a third and the 
corresponding minima. The cold wall cannot be recognized 
upon it, probably for the want of one or two, more positions. 

The form of the bottom delineated on these two sections, name- 
ly' the Charleston and Cape Florida sections, is remarkable and 
applies to the sections between them as far as explored. First is 
a gentle slope, then a sudden descent, a second steep pitch to a 
considerable depth, a range of hills, a valley and a second range. 

The correspondence of these features with the bands of tem- 
perature is plainly marked. The cold water lies in the valleys 
and passing along the bottom rises upon the tops of the hills. The 
discovery of this range of hills was made at nearly the same time 



12 Prof, Baches Lecture on the Gulf Stream. 

b}' Lieut. Maffitt on the Charleston section and by Lieut. Craven 
on the St. Simon's section. Diagram No. 9, Plate I, shows this 
connection in a very striking manner as does also No. 7, Plate II, 
and the figure of the bottom of the straits of Florida, shows why 
there are no bands formed prior to passing Cape Florida, in other 
words, why the regimen of the stream is different in the straits 
and in the Atlantic. In the straits we see (No. 9, Plate II) that 
after leaving the United States shore and the comparatively flat 
surface extending to the reefs, there is a rapid descent toward the 
Cuban side of the strait, the axis of the Gulf Stream being found 
in the deep hollow of that side of the strait. 

These results, with a more elaborate discussion of them, were 
presented at the last meeting of the Association. It would seem 
from the configuration of the bottom, that the cold stream at the 
bottom of the straits of Florida divides, one portion passing to the 
north and west into the Gulf of Mexico and the other around the 
western end of the Island of Cuba. That the polar stream still 
occupies the bottom of the strait is shown by temperature of 
35° Fahr. being reached at 600 fathoms from the surface off 
Havana. 

Do these bands correspond throughout their length to the form 
of the bottom of the sea? This is not yet made out, many as 
have been the attempts to reach the considerable depths off the 
more northern sections. Three officers have attempted to sound 
out the Cape Cod section, but the cold wall is all that has been 
reached thus far. The range of hills nearest to the coast, has 
been traced from the coast of Georgia by Commander Sands to 
off Cape Lookout. 

III. The Cold Wall. 

The cold wall extends with varying dimensions and changes 
of its peculiar features, all along the coast w r here the stream has 
been examined. A diagram showing the features of the cold 
wall on the various Atlantic sections and those of the straits of 
Florida is given in No. 10, Plate I. Table No. 1 shows the dis- 
tance of the cold wall from the coast and the dimensions of the 
Atlantic bands of the Gulf Stream. 

The table shows that at Cape Florida and Cape Hatteras the cold 
wall is nearest to the coast. The distance of the axis of the stream 
from the coast will be found by adding half the numbers in the sec- 
ond column to those in the first column. It is obvious from these 
numbers, when taken in connection with the longitudes of the 
points where the sections originate, that the earth's motion is not 
the sole determining cause of the direction of the axis of the 
stream, a result which a more elaborate investigation of the move- 
ments from parallel to parallel confirms. In the portions of its 
course between Cape Florida and Mosquito inlet (8 J° of latitude) 
the curve is actually slightly to the westward. 



Prof. Baches Lecture on the Gulf Stream. 



13 



Table 1. — Distance of the cold wall from the shore, and widths of the several bands 
of cold and warm water in the Gidf Stream, measured on the lines of the Sections. 



Names of Sections. 



Sand j Hook.. . 

Cape May , 

Cape Henry 

Cape Hatteras. , 

Cape Fear 

Charleston 

St. Simons 

St. Augustine... . 
Cape Canaveral. 
Cape Florida. . . 



8- « . 


JL O . 


T3 s- 

<n © 


TS 

a 


^ s 


3S 


iss 


SS 






6 E-2 


of 

•S s 


5°° i 


5 e-o 










2=T3 

£s8 


£e 


> _ a. 




"2 x £ 
fell 


Ss2 
Ml 

Tndef. 


240 


60 


30 


37 


127 


60 


50 


125 


55 


30 


40 


125 


70 


65 


70 


95 


45 


32 


47 


124 


80 


60 


50 


30 


47 


25 


45 


117 


37 


75 


70 


60 


30 


20 


37 


87 


30 


60 


25 


62 


25 


15 


30 


67 


26 


35 


— 


87 


25 


13 


20 


58 


25 


25 


— 


70 


20 


13 


12 


47 


22 


20 


— 


35 j 


20 


— 


— 


35 


14 


12 


— 


10 


25 


— 


- 1 


25 


5 


— 1 


— 



Note. — The width of the bands beyond the 2d maximum, and north of Cape Hat- 
teras are somewhat indefinite. 

The table shows a width in the Ghilf Stream proper along the 
Atlantic coast of from 25 miles off Cape Florida to 127 miles 
off Sandy Hook. The warm water at say fifteen fathoms, is 
from 30 to 150 miles in width. The stream widens each way 
from Cape Florida. These several divisions of the Atlantic 
stream lose a portion of their distinctness as we pass northward 
and eastward, the stream widening. 

IV. Limit of Accuracy of the Determinations. 

There are two modes by which the limits of accuracy of these 
results may be tested, by one of which their permanency is also 
tried. In this latter mode the sections are run over in different 
years, or in the same year by different officers, so as to connect 
the observations of one year with those of the next, or of one 
officer with that of another. Table No. 2 shows that the relative 
results are reproduced from year to year with, less variability 
than those of the mean temperature of the section ; and hence 
the permanency of the bands and the possibility of observing 
them with the requisite precision must be admitted. On the 
Cape Henry section which was explored three times, the position 
of the cold wall and of the axis of the stream were reproduced 
within 5J miles and those of the succeeding points of maxi- 
mum and minimum temperatures within 7-J- miles. As the posi- 
tions at sea are liable to an uncertainty of some three to five 
miles it must be admitted that the permanency of the bands 
and the accuracy of the observations of them are fully proved. 

The Cape Henry section was run over by Lieuts. Gr. M. Bache, 
S. P. Lee, and Eichard Bache, the Hatteras section by Lieuts. 
Eichard Bache and J. N. Maffit, and the Charleston section by 
Lieuts. J. N. Maffit and T. A. Craven. 



14 



Prof. Bache s Lecture on the Gulf Stream. 



Table 2. — Table showing the probable uncertainty in the determination of maximum 
and minimum points, by running the same section over in different years by differ- 
ent observers. 

Cape Henry Section. 



Mean distances hom the shore in miles 
from the curves representing the groups 



Dates and names of observers. 



Lt. G. M 


Bache 
Lee, 
che, 


1846 


" S. P. 


1 847 


" RBa 


1848 






Means 


for three years. 



Probable error for each year. 











a 












> a 




a . 


c K 


E 


E 


,s 


2^ 


.2 S 


8'i 


g CS 

CO 


■g 


15 


'a 


O o 


< 






H 


h 




93 


135 


187 


218 


260 


320 


369 


91 


146 


185 


215 


291 


337 


338 


97 


146 


180 


197 


287 


3 '.'8 


*7l» 


84j 142| 184| 210| 279| 328| 370 



5-85| 4-27 i 2'42 |7-62|ll'hl|5-71 17-18 



Cape Hatter as Section. 


Lt. R. Bache, 1848 


— 


901 

75| 


134 
125 


1621 

157| 


214 
211 


286 
256 


355 
322 


" J. M. Maffit, 1 853 




Means for two years 


-1 82| 


129 


159| 


212 


266| 338 




Probable error for each year 


-i 6-4| 


43 


I 2-4 ! 


1-5 


15| 16 




Means for both sections 


5-85| 5-3| 


34 


6-0| 


6-4 


| 1'04|1-16 



Average uncertainty of maxima and minima, 6-9 miles. 
" " cold wall and axis, 5*5 " 

" " all the other points, 7 '4 " 

The other mode of testing the result is by the comparison of 
the remarkable points in the different sections, each one belong- 
ing to a different position and therefore being entirely indepen- 
dent of the other in its determination. It is established as a 
general law that this cold wall and axis of the hottest water 
change their position from the surface to the depth of six hun- 
dred fathoms slowly and by an ascertained progression, and that 
the succeeding maximum and minimum points are at the same 
distance from the shore, nearly, at different depths, or in a verti- 
cal line at all the different depths. The positions of these points as 
shown by the observations at different depths become thus the 
test of the permanency of their positions and of the accuracy with 
which they have been ascertained. Table 3 gives the. prob- 
able error of the mean of the determinations of each point in- 
cluding the cold wall minimum, the axis maximum, and the suc- 
cessive minima and maxima to the fourth minimum inclusive. 
These results show that the cold wall minimum is ascertained, on 
the average, within 83 mile, the axis maximum within two 
miles and a half, the second minimum within two miles and a 
half, the second maximum and third minimum and third 
maximum, within four miles, and the fourth maximum within 
eight and a half miles, all being satisfactory except the last, 
which of course is in reality loosely denned. The Hatteras re- 
sult for the axis of the stream, makes the probable error con- 
siderably larger than it would otherwise be, probably from the 



Prof. Bache's Lecture on the Gulf Stream. 



15 



fact that the proximity of the bottom of the sea, makes the 
result less permanent than in the other cases. Without this re- 
sult the mean probable error would be 11 mile. 

Table 3. — Recapitulation, showing the value of the probable error of determination 
of the bands for each section and the average of the whole. 



Sections. 


1st min. 


1st max l2d min. 


2d max. 


3d min 


3d max i 


4th min. 




Probable e 


rors>. 






Sandy Hook 


•82" 
•84 

1-25 

•52 
•95 


•75 
1-25 

•61 
6'77 
1-25 
1-57 

•74 

•51 
1*69 


2-54 

•55 

6-36 

•72 

1-27 

•44 

•39 


3-94 
1-57 
1-70 
931 

2-09 
•41 
•44 


7-99 

1-06 
5-69 
2-98 
2-40 

•55 


4-03 

•94 

623 

3-49 

•82 


4-87 
3-42 

1337 


Cape May 


Cape Henry, 3 years 

Cape Hatteras, 2 years, 

Cape Fear 




St. Augustine 


Cape Canaveral 




1 Mean probable error 


•83 


249 | 2-49 


4-00 


4-U1 


3-71 


8-45 



While these results are so permanent, the mean temperatures 
of the sections change considerably from year to year. The 
average temperature between the surface and 400 fathoms be- 
yond, or outside of the cold wall on the Sandy Hook section in 
1846, was as high as that on the Cape Henry section in 1848, 
and that on the Cape Fear section in 1853, within a degree of 
that of the St. Augustine section in 1853, while the Cape Hatte- 
ras section in 1848 and in 1853, differed two degrees in mean 
temperatures. Again the temperatures from the surface to 30 
fathoms just below the axis of the stream in the Sandy Hook 
section in August 1846 was either as high or higher than those 
on the Canaveral section in June 1853. In general the Cape 
May section in 1846 and the mean of the Cape Henry section of 
1846, 1847 and 1848 are warmer at the same depths than the 
sections south of it were in 1848 and 1853. 

These results show that there are great changes in temperature 
from year to year, and probably from season to season. Some 
progress has been made in connecting these results in a general 
way with the changes of weather in the Gulf of Mexico. 

The depths at which the results are easily determined and 
where they are characteristic and as permanent as the phenomena 
permit is thirty fathoms. 

V. Figure of the Bottom of the Sea, below the Gulf Stream. 

We have seen that in cross sections there is a great resem- 
blance in the bottom of the sea off our coast to the region of land 
more removed from the coast-line in the interior. The top of 
the first range of hills, (see Diagram No. 9, Plate I,) is 1500 feet 
above the valley to the eastward of it, distant 12 miles ; and the 
top of the second range 600 feet above the same valley, distant 
15 miles. The first slope is 125 feet, and the second is 40 feet, 



16 P ro f- Backers Lecture on the Gulf Stream. 

to the mile. The bottom of the sea from the Tortugas section to 
that of Cape Florida, rises from 800 to 325 fathoms, and from 
the same point descends, in passing northward and eastward. 
The Cape Florida section showed that there then was present a 
ridge of comparatively cold water since the division into bands 
should apply along the stream as well as in the direction of its 
cross sections. The temperature of 40° is in fact reached on 
that section at 300 fathoms, and, as well as can be judged from 
the results in the separate sections there are divisions of this 
sort. The diagram No. 2, Plate II, shows where the curves of 
50° and 45° are found upon the different sections and indicates 
a rise on the Charleston section and a sharp descent from 
Charleston to Cape Fear. 

VII. General features of the Gulf Stream. 

Upon the general diagram now presented to the members, 
(Plate III,) the general features of the Gulf Stream are repre- 
sented from the Tortugas to the Cape Cod Section. Passing 
along the Cuban coast the temperature in June was found 
to be about 84° or 8° above the mean temperature of Key 
West, as given by the Surgeon General's report. The cur- 
rent here is feeble, but sufficient to cause it to be sought by 
sailing vessels making to windward and even by steamers. Is- 
suing from the straits of Bernini, the stream is turned northward 
by the land which confines and directs its course. Its effective 
velocity is not derived from difference of temperature, as the 
observations abundantly show, the greatest relative differences 
being in fact crosswise of the stream. The direction is here a 
little west of north and the velocity is from 3 to 5 miles per 
hour. The temperature bands now begin. The bottom of the 
sea which was one slope and counter slope, across the Florida 
Straits, is here corrugated ; the depth instead of being unfath- 
omable, as has heretofore been supposed, is but 325 fathoms, in 
which depth the two currents, from the poles near the bottom 
and from the Gulf at the top, must pass each other. While the 
surface water is above 80° that near the bottom is as low as 40°. 

The stream just north of Mosquito inlet begins to bend to the 
eastward of north, and off St. Augustine has a decided set to the 
eastward. While flowing thus onward the warm water seeks 
the sides of the channel overflowing towards the coast of Florida, 
and towards the Bahamas, but not as rapidly as it moves on 
north. Between St. Augustine and Cape Hatteras the set of 
the stream and the trend of the coast differ but little, making 5 
degrees of easting in 5 degrees of northing. At Hatteras it 
curves to the northward and then runs easterly, making about 3 
degrees of northing in 3 degrees of easting. In the latitude of 
Cape Charles it turns quite to the eastward having a velocity of 
between one and one mile and a half the hour. 



Prof. Bache's Lecture on the Gulf Stream. 71 

That this curve follows the general sweep of the coast under 
water, appears most probable, the coast line, the curve of 100 
fathoms and the ranges of hills discovered by Lieuts. Maffitt and 
Craven all seem to indicate it. That the direction of the stream 
is given in a general way by the configuration of the bottom of 
the sea, is hardly possible to doubt, while admitting that it 
receives modification from other, and perhaps more general, cau- 
ses. The after progress of this mighty stream, and of its branches 
if it does divide, remains yet to be traced and so also its heading 
in the Grulf of Mexico. 

I forbear to mingle doubtful speculation upon causes, with the 
inductions in regard to temperatures, which it has been the object 
of these observations to supply and of this lecture to bring to 
your notice. 






GULF STREAJ 



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